1. Field of the Invention
The present invention relates to a recording head that is applied to a recording apparatus configured to perform a recording operation by discharging a recording liquid such as ink.
2. Description of the Related Art
FIG. 19 is a perspective view illustrating an ink discharge surface of a recording head 1000 mounted on a general ink jet recording apparatus. Then, FIG. 20 is a perspective view illustrating the opposite side of the ink discharge surface shown in FIG. 19.
A recording element substrate 1100 provided in the recording head 1000 heats ink by an electric thermal conversion element having a heating resistor, and discharges ink droplets from a discharge port 1101 by an action of film boiling.
An electrical wiring substrate 1200 is electrically connected to the recording element substrate 1100 assembled to an open portion, and is configured to apply a driving signal input from an apparatus body (not shown) via a contact portion 1201 to the recording element substrate 1100. The electrical connection portion between the recording element substrate 1100 and the electrical wiring substrate 1200 is protected by a sealing material 1300.
A support member 1400 is used to hold and fix the recording element substrate 1100 and the electrical wiring substrate 1200 thereto. Further, the support member 1400 includes an ink injection port 1401 that is used to supply ink to the recording element substrate 1100. The support member 1400 has a structure in which a filter 1500 and a sealing rubber 1600 are provided in the ink injection port 1401, and a passage is provided to guide ink stored in an ink tank to the recording element substrate 1100.
FIG. 21 is an enlarged view illustrating a portion A of FIG. 19, where the sealing material 1300 is visibly depicted for convenience of description. FIG. 22 is a plan view illustrating a part shown in FIG. 21. FIG. 23 is a cross-sectional view taken along the line 23-23 of FIG. 22.
The recording element substrate 1100 includes a heater board 1104 which has an electric circuit with a heating resistor and an orifice plate 1103 which has a discharge port 1101. Plural electrodes 1102 are provided in the heater board 1104.
In general, the electrical wiring substrate 1200 is formed of a single or double layered FPC board (flexible printed circuit board) or a TAB film. For example, the FPC board has a structure in which interconnections 1202 are provided on a surface of a base film 1203, and a cover film 1204 is provided on the surface. An interconnection portion exposed from an open portion of the cover film is generally subjected to gold-plating to serve as an electrical connection terminal.
As shown in FIG. 24, electrodes 1102 of the recording element substrate 1100 and interconnections 1202 of the electrical wiring substrate 1200 are electrically connected to each other by gold wires 1700 of wire bonding. The electrical connection portion is protected by the sealing material 1300. The sealing material 1300 is provided to cover from the orifice plate 1103 to the cover film 1204.
At the time when the sealing material 1300 is coated on an electrical connection portion, dummy wires not used for electrical connection other than main wires used to drive the recording head may be used to prevent the sealing material 1300 from being dropped, assist a coating process, and reinforce a sealing portion.
Japanese Patent Application Laid-Open No. H07-335680 discloses a semiconductor device that includes a dummy wire having a top point higher than a top point of a wire used in practice for electrical connection. This semiconductor device is sealed by receiving a plate-shaped tablet resin dropped downward using the dummy wire.
Japanese Patent Application Laid-Open No. H08-336963 discloses an ink jet recording head in which a dummy wire is provided at the outside of a wire group. In this ink jet recording head, the sealing material 1300 coated on an electrical connection portion spreads in the dummy wire, thereby protecting the outside of the main wires.
The two-dotted chain line of FIG. 23 is an imaginary line 1301 that represents the shape of the surface of the sealing material 1300. Since the ink jet recording head has a characteristic in which recording quality becomes more improved as a gap between the recording head and a recording medium such as a recording sheet becomes narrower, it is important that the height h5 of the sealing material 1300 protruding more than the orifice plate 1103 is set as low as possible. For this reason, the height h5 of the sealing material 1300 needs to be managed to be a predetermined value or less.
However, in the sealing method of the semiconductor device disclosed in Japanese Patent Application Laid-Open No. H07-335680, since the dummy wire absorbs an impact generated by the dropping of the tablet resin, there are concerns that the dummy wire is deformed and the height of the sealing material is not stably maintained.
Further, the ink jet recording head disclosed in Japanese Patent Application Laid-Open No. H08-336963 controls the height of the sealing material by the coating amount of the sealing material and the spreading degree of the sealing material. However, since the sealing material has a difference in physical property value of viscosity or the like according to a manufacturing lot or a variation in time, the height of the sealing material needs to be frequently examined and the coating condition needs to be adjusted in order to maintain the uniform height of the sealing material.
Therefore, the invention is made in view of such technical problems of the related art, and achieves the following purposes.
That is, an object of the invention is to improve a recording quality of a recording head by rapidly performing a feedback to a sealing process and reducing a difference in the height of a sealing material due to a configuration capable of simply determining whether a height of a sealing material of the recording head is more than a predetermined upper limit position.
Further, there is another problem in that a coating portion of an electrical connection portion, that is, the coating thickness t7 of the gold wire 1700 formed in a protruding manner is thinned when the height of the sealing material is too low, so that electrical reliability may be degraded.
Accordingly, a second object of the invention is to provide a configuration capable of simply determining whether the height of the sealing material of the recording head is lower than the predetermined lower limit position. Therefore, electrical reliability of the recording head may be improved by rapidly performing a feedback to the sealing process, and reducing a difference in the height of the sealing material.